arXiv subjects

Camilo Delgado-Correal

Publications and source records attributed to Camilo Delgado-Correal.

7 recordsLinked to original sources

arXiv2026

Determination of $H_{0}$ with a Photometric AGN Golden Sample derived from a joint SN Ia-QSO cosmological reconstruction

The current tension between early and late-Universe determinations of the Hubble constant motivates the development of independent high-redshift distance tracers. Quasars, as luminous active galactic nuclei - AGNs, provide a promising route through the empirical relation between their X-ray and ultraviolet luminosities.We construct a joint Type Ia supernova-quasar Hubble diagram and investigate whether a statistically selected quasar subsample can define a preliminary golden sample for future AGN standardization. We combine calibrated Type Ia supernovae with SDSS DR14 quasars and infer the cosmological parameters from the posterior distribution of a joint model. Posterior medians and credible intervals are obtained from the marginalized distributions. We further define redshift-dependent quasar pools from SDSS queries and select the most representative sources in each bin using a multivariate statistical-distance criterion based on redshift, optical magnitudes, and SDSS colors. The posterior analysis yields $H_0 = 71.76^{+1.67}_{-1.31}\,\mathrm{km\,s^{-1}\,Mpc^{-1}}$ and $Ω_m = 0.294^{+0.014}_{-0.012}$. The statistically selected quasar candidates reproduce the reference Hubble diagram with small residual dispersion across multiple redshift intervals and remain broadly distributed across the SDSS angular footprint without evidence of strong artificial clustering induced by the selection procedure.

physics.gen-ph↗

arXiv2024

Evaluating a Sigmoid Dark Energy Model to Explain the Hubble Tension

In this study we analyze Type Ia supernovae (SNe Ia) data sourced from the Pantheon+ compilation to investigate late-time physics effects influencing the expansion history, $H(z)$, at redshifts $(z < 2)$. Our focus centers on a time-varying dark energy (DE) model that introduces a rapid transition in the equation of state, at a specific redshift, $z_a$, from the baseline, $Λ= -1$, value to the present value, $w_0$, through the implementation of a sigmoid function. The constraints obtained for the DE sigmoid phenomenological parametrization have broad applicability for dynamic DE models that invoke late-time physics. Our analysis indicates that the sigmoid model provides a slightly better, though not statistically significant, fit to the SNe Pantheon+ data compared to the standard LCDM alone. The fit results, assuming a flat geometry and maintaining $Ω_m$ constant at the 2018-Planck value of $0.3153$, are as follows: $H_0 = 73.3^{+0.2}_{-0.6}$ km s$^{-1}$ Mpc$^{-1}$, $w_{0} = -0.95^{+0.15}_{-0.02}$, $z_a = 0.8 \pm 0.46$. The errors represent statistical uncertainties only. The available SN dataset lacks sufficient statistical power to distinguish between the baseline LCDM and the alternative sigmoid models. A feature of interest offered by the sigmoid model is that it identifies a specific redshift, $z_a = 0.8$, where a potential transition in the equation of state could have occurred. The sigmoid model does not favor a DE in the phantom region ($w_0 < -1$). Further constraints to the dynamic DE model have been obtained using CMB data to compute the distance to the last scattering surface. While the sigmoid DE model does not completely resolve the $H_0$ tension, it offers a transition mechanism that can still play a role alongside other potential solutions.

astro-ph.CO↗

arXiv2013

Study of shock wave dynamics produced by interaction of a fireball with the surrounding medium to it, to explain the x-ray afterglow of Gamma Ray Burst-GRBs

The Gamma-Ray Bursts - GRBs are one of the most energetic astronomical events in the universe that have not yet an adequate explanation of what kind of mechanism is carried out. This question motivates the astronomical community to do radiation measurements associated with the GRBs. They also are doing physical models to explain the temporal behavior of these observational results. The community are looking for an appropriate explanation of GRBs origin. This thesis presents an astrophysical model that includes an hydrodynamic and radiative aspects. This model studies the temporal evolution of a wave carries an expansive ultra-relativistic adiabatic fluid. Additionally, this thesis present a comparison between model with GRB 050525 observational behavior. It is found that the blast wave radius R shows an increase in the time: R \approx t^{1/4}, the Lorentz gamma factor of charged particles that are in ultra-relativistic fluid decreases significantly over time and the theoretical flow of radiation: F_ν \approx t^{-β} with β around 1 fits very well with the two slopes of the x-ray afterglow light curve of GRB 050525.

astro-ph.HE↗

arXiv2012

Physical aspects to consider in radiometric calibration of satellite images

It does a revision about the physical principles involved in digital processing of satellite images, more specifically in radiometric calibration of them. It shows a conceptual description of the interaction between radiation and atmosphere and radiation and soil in order to help the reader understand in more detail which means the information contained in satellite images.

physics.ao-ph↗

arXiv2012

Radiometric in-situ calibration of satelital sensors of Earth observation using a spectroradiometer

By using the satelital information of Earth observation unloaded by a station constructed in the country and reflectances measurements of the soil, we found the total radiation attenuation of the atmosphere for a small region of the Colombian territory. It was necessary to use the Fourier's theory that describes the ideal filters of signals to find the transfer functions between the spectral response of an spectroradiometer and the satelital sensor, whose radiative sign we are going to calibrate. After that, we used the reflectance spectrum of the soil taken with our spectroradiometer, the information in digital numbers (DN) of a pixel of the satelital image of the same region at the same time, and using again the theory of ideal filters we found the transfer function between the responses of both sensors to the radiance of the soil. The relation between both signals provides us the total intensity of the radiation attenuation of the atmosphere for pixel, which is fundamental to do a radiometric calibration of the whole image. We found a factor of atmosphere attenuation of the radiation (λ between 430nm to 830nm) from the soil(of the pixel surface) of H_{Total(λ)Atmosphere} = 1,435x 10^{-3}.

physics.ao-ph↗

arXiv2012

Computational study of atmospheric transfer radiation on an equatorial tropical desert (La Tatacoa, Colombia)

Radiative transfer models explain and predict interaction between solar radiation and the different elements present in the atmosphere, which are responsible for energy attenuation. In Colombia there have been neither measurements nor studies of atmospheric components such as gases and aerosols that can cause turbidity and pollution. Therefore satellite images cannot be corrected radiometrically in a proper way. When a suitable atmospheric correction is carried out, loss of information is avoided, which may be useful for discriminating image land cover. In this work a computational model was used to find radiative atmospheric attenuation (300 1000nm wavelength region) on an equatorial tropical desert (La Tatacoa, Colombia) in order to conduct an adequate atmospheric correction.

physics.ao-ph↗

arXiv2010

How is the Monoclonal Antibodies Kinetic Affected by Changes of Their Physical Parameters?

The study of monoclonal antibodies (MAb) is a field of great interest to science medicine, for example, anti-TNF agents (infliximab and adalimumab) represent an important tool for the management of autoimmune and inflammatory disorders. In this work we focus on the physical description of the transport kinetics of MAb in a fluid with laminar flow and parabolic profile. To simulate the kinetics of the MAb, standard equations were solved numerically (using The Verlet algorithm) to calculate the motion of a particle with a spherically symmetric inside of parabolic laminar flow, in order to find the time evolution of the antibody velocity in blood plasma in function of the increase of the radius, mass and density of the MAb, and the fluid pressure in blood vessels. In the case of we fixed the value of the antibody density, their kinetics increased when the pressure in the vessels increased. When we fixed the pressure in the vessels we found: if we reduce the antibody radius their kinetics increased, and when we increase antibody density we found that their kinetics also increased.

physics.bio-ph↗